INTEGRATED OPTICAL DISPLACEMENT SENSOR WITH 4 QUADRATURE PHASE-SHIFTED OUTPUT SIGNALS

An integrated optical displacement sensor with multiphase detection fo r highest resolution displacement measurements is presented. The senso r delivers ideally four intensity-coded pi/2 phase-shifted signals, wh ich allows one to overcome the difficulties of intensity and contrast variation of the signals by simple electronic processing. The sensor h ead is realized by ion exchange on glass substrate, which is completel y passive and therefore immune to electromagnetic interference. The us e of a HeNe laser allows a measurement range of several metres with an accuracy of up to 10(-7) in a stabilized environment. Simple fringe c ounting permits a precision of up to lambda/8, corresponding to 79 nm. For the highest precision measurements beyond fringe counting, this r esolution can be further enhanced by fringe interpolation.